It was not to the Académie des Sciences, as is generally believed, that Pasteur sent the paper on lactic fermentation, the fifteen pages of which contained such curious and unexpected facts. With much delicacy of feeling, Pasteur made to the Lille Scientific Society this communication (August, 1857) which the Académie des Sciences only saw three months later. How was it that he desired to leave this Faculty at Lille to which he had rendered such valuable service? The Ecole Normale was going through difficult times. “In my opinion,” wrote Pasteur with a sadness that betrayed his attachment to the great school, “of all the objects of care to the authorities, the Ecole Normale should be the first; it is now but the shadow of its former self.” He who so often said, “Do not dwell upon things already acquired!” thought that the Lille Faculty was henceforth sure of its future and needed him no longer. Was it not better to come to the assistance of the threatened weak point? At the Ministry of Public Instruction his wish was understood and approved of. Nisard had just been made Director of the Ecole Normale with high and supreme powers; his sub-director of literary studies was M. Jacquinet. The administration was reserved for Pasteur, who was also entrusted with the direction of the scientific studies. To that task were added “the surveillance of the economic and hygienic management, the care of general discipline, intercourse with the families of the pupils and the literary or scientific establishments frequented by them.” The rector of the Lille Faculty announced in these terms the departure of the Dean: “Our Faculty loses a professor and a scientist of the very first order. You have yourselves, gentlemen, been able to appreciate more than once all the vigour and clearness of that mind at once so powerful and so capable.”